1. Field of the Invention
The present invention relates to an apparatus and method for an adaptive resistor termination network for use in tuning an integrated network to provide a desired value of resistance.
2. Description of the Related Art
Documents known in the art describe how the output impedance of a voltage driver can be modified by using multiple parallel pull up and pull down transistors in an output driver and selecting the number of active devices to achieve the required output impedance (as disclosed in U.S. Pat. No. 5,134,311). U.S. Pat. No. 6,026,456 uses a termination network with a higher impedance than the bus impedance which it is controlling to optimise the bus impedance.
One possible approach is one using a linear technique to trim the main resistor in termination system. Although relatively simple to implement, this system has the disadvantage of static power consumption which can be significant in low power applications. In addition, when multiple termination networks are needed to be controlled from a single termination system then an analog voltage needs to be distributed to these networks, and this is susceptible to interference and error.
U.S. Pat. No. 5,652,538 describes a digital solution problem using a network where parallel elemental conductances are switched in and out of circuit by a digital controller to attain the required impedance.
It would therefore be desirable to have an apparatus and method for an adaptive resistor termination network for use in tuning an integrated network to provide a desired value of resistance with improved characteristics of error-resistant operation, tunability and low power-consumption.